This invention relates to a multi-directional key switch assembly having a central switch, and, more particularly, to a multi-directional key switch assembly useful for depressing a plurality of different kinds of switches and maintaining them simultaneously in an ON-state.
A typical example of the prior art multi-directional key switch assembly, as shown in a cross-sectional view in FIG. 1, comprises a central switch 77 and a plurality of peripheral switches 79 arrayed on a circle around the central switch and each including a fixed contact pair, all the switches being disposed on a printed-circuit board 80, as disclosed in Japanese Patent Publications Kokai Nos. 7-141962 and 7-141963, for example. This multi-directional key switch assembly is configured such that the central switch 77 may be actuated by depressing the key top 72 downwardly and that any one or more of the peripheral switches 79 may be actuated by tilting the key top 72 radially outwardly.
While this prior art multi-directional key switch assembly is configured such that the central switch 77 may be actuated by depressing the key top 72 downwardly and that a plurality of the peripheral switches 79 may be actuated by pressing and tilting the key top 72 radially outwardly, it has only two kinds of switches, the central switch 77 and the plurality of peripheral switches 79 circumferentially arranged around and outward of the central switch. While these peripheral switches 79 are differentiated from each other by the directions in which the key top 72 is tilted for actuation, it may be said that they are in the same rank and the same kind.
Another example of the prior art multi-directional key switch assembly, the arrangement of fixed contacts of which is shown in a plan view in FIG. 2A, comprises an up-to-down array of linearly aligned switches each including a fixed contact pair 20u1, 20u2, 20u3, 20d1, 20d2, 20d3 and a left-to-right array of linearly aligned switches each including a fixed contact pair 20l1, 20l2, 20l3, 20r1, 20r2, 20r3. As shown in FIG. 2B, these switches are accommodated in a case 12 and are adapted to be operated by a criss-cross key top 14 having operating tabs 14u, 14d, 14l and 14r. The arrangement is such that the key top 14 may be tilted in a desired direction and at an angle of desired degrees by press-operating the operating tabs 14u, 14d, 14l, 14r whereby one or more of the plurality of switches may be succesively turned ON and maintained in that ON-state depending on the direction and the degree of angle of tilting. Such multi-directional key switch assembly is disclosed in Japanese Patent Publication Kokai No. 2-41342, for example.
In this prior art switch assembly the fixed contact pairs 20u1, 20d1, 20l1 and 20r1 arrayed on the same circle constitute a group of the same kind of switches. Likewise, the fixed contact pairs 20u2, 20d2, 20l2 and 20r2 arrayed on the same circle constitute a second group of the same kind of switches. And the fixed contact pairs 20u3, 20d3, 20l3 and 20r3 arrayed on the same circle constitute a third group of the same kind of switches. It will thus be understood that a group of switches belonging to the same kind are common to all in that the degree of angle to which the key top 14 is required to be tilted to actuate the switches.
A wide variety of multi-directional key switch assemblies other than those as described above have been developed and are in use.
In the prior art example illustrated in FIG. 1, excluding the central switch 77, as for the kind of switch, there is only one kind of switch, that is, the peripheral switches 79 which require the same angle of tilting of the key top 72 to effect the ON-actuation. In order to form another kind of switch having a different nature in addition to the peripheral switches 79, it is required that an additional array of switches be arranged on a circle outward of the peripheral switches, which necessitates enlarging the entire switch structure in its outer diameter. Representative of such example is the prior art key switch assembly shown in FIGS. 2A and 2B comprising three kinds of switches having different natures. However, since these three kinds of switches are formed on three different circles, it can hardly be said that such an arrangement has a good space factor.